Question: Evaluate the following expression when $b = 2$ and $a = 7$. $9$ $b$ $ + 7$ $a$ $ - 4$
Solution: Substitute $2$ for ${b}$ and $7$ for ${a}$ $ = 9{(2)} + 7{(7)} - 4 $ $ = 18 + 49 - 4 $ $ = 63$